Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) have been applied as main deposition techniques for producing thin films for semiconductor devices. These methods enable the achievement of conformal films (metal, oxide, nitride, silicide, etc.) through fine tuning of parameters during the deposition processes. Mainly the film growth is controlled by chemical reactions of metal-containing compounds (precursors) and the development of optimum precursors is essential under prediction of their properties and reaction processes.
Films of metal and metal silicide, particularly manganese, iron, cobalt, nickel, and ruthenium, are becoming important for a variety of electronics and electrochemical applications. For example, cobalt thin films are of interest due to their high magnetic permittivity. There are many reports of using cobalt thin films to form cobalt disilicide (CoSi2) for Ohmic contacts owing to its low resistivity in front-end-of-the-line processing of semiconductor devices. Cobalt containing thin films were recently studied as Cu/low-k barriers, passivation layers, and capping layers for ultra-large scale integrated devices.
Synthesis methods of substituted silyl or halide cobalt tetracarbonyl complexes (R3SiCo(CO)4) are known (Sisak et al., Formation and Multinuclear Magnetic Resonance Investigation of Silylammonium Tetracarbonylcobaltate Contact Ion Pairs, Central European Journal of Chemistry, 4(2) (2006) pp. 299-316; Begum et al. Synthesis, Reaction and Thermal Decomposition of a Silicon-Cobalt Bonded Compound, Journal of Bangladesh Academy of Sciences, Vol. 17, No. 2 (1993) pp. 201-205; Chatani et al., Cobalt Carbonyl Catalyzed Reactions of Esters and Lactones with Hydrosilane and Carbon Monoxide. A Novel Synthetic Method for the Introduction of the Siloxymetahylidene Group, J. Am. Chem. Soc. (1986) 108, pp. 7361-7373; Chatani et al., A New Entry to π-Allylcobalt Tricarbonyls Using (CH3)3SiCo(CO)4, Tetrahedron Letters, Vol. 24, No. 50 (1983) pp. 5649-5652; Reichel et al., Photochemistry of Cobalt Carbonyl Complexes Having a Cobalt-Silicon Bond and Its Importance in Activation of Catalyis, Inorg. Chem. 19 (1980) pp. 3858-3860; Bradley et al., Reaction of Octacarbonyldicobalt with Organosilanes, -germanes, and -stannanes. Formation, Properties, and Vibrational Spectra of (Trimethylgermyl)tetracarbonylcobalt and Related Complexes, Journal of the Chemical Society, Dalton Transactions: Inorganic Chemistry (1974) 3, pp. 264-9; Ingle et al., Cobalt to Oxygen Migration of the Trimethylsilyl Group in Trimethylsilylcobalt Tetracarbonyl, Journal of the Chemical Society, (1973) 14, pp. 497-498; Morrison et al., Trichloro-, Trimethyl-, and Trifluorosilylcobalt Tetracarbonyl, Inorganic Synthesis, 13 (1971) pp. 65-73; Baay et al., Trimethyl- and Trichlorosilylcobalt Tetracarbonyls and the Hydrosilation of Ethylene, Inorganic Chemistry, Vol. 8, No. 4 (April 1969) pp. 986-994; MacDiarmid et al., Properties of Silicon Derivates of Cobalt, Manganese, and Iron Carbonyls, Pure and Applied Chemistry (1969) Vol. 19, Issue 3, pp. 431-438; Baay et al., Synthesis and Properties of Trimethylsilyl Cobalt Tetracarbonyl and Related Compounds, Inorg. Nucl. Chem. Letters, Vol. 3 (1967) pp. 159-161).
Ethyl substituted silyl cobalt tetracarbonyl complexes (Et3SiCo(CO)4) are also disclosed in the literature (see, e.g., Sisak et al., Central European Journal of Chemistry, 4(2) (2006) p. 300). However, details of the synthesis conditions and chemical and physical properties of ethyl substituted silyl cobalt tetracarbonyl are not included in the references.
Silyl cobalt tetracarbonyl complexes (R3SiCo(CO)4), wherein R is an hydrogen (H), methyl (Me) and chlorine (Cl) are also known as precursors for cobalt-containing films (Prokap et al., nm-Co2Si, CoSi, CoSi2 silicide films from the single source precursor CoSiCl3(CO)4 in the presence of SiH4, Thin Solid Films, 359 (2000) pp. 39-45; Kodas et al., The Chemistry of Metal CVD, Wiley-VCH (1994) Section 9.2 Classification of Precursors; Aylett et al., Chemical Vapour Deposition of Transition-Metal Silicides by Pyrolysis of Silyl Transition-Metal Carbonyl Compounds, J.C.S. Dalton (1977) pp. 2058-2061; Advances in Inorganic Chemistry and Radiochemistry, (1982) pp. 107-110).
The thermal stability of the precursor and ease of precursor synthesis are important in selecting a precursor suitable for commercial applications, as well as the final film properties of the films deposited by the precursor. Cl3SiCo(CO)4 is more stable than H3SiCo(CO)4 (Prokap et al., at 39), but Cl may cause corrosion problems in the film and in deposition facilities, such as the supply lines, chamber and exhaust line in general.
A need remains for cobalt compounds suitable for deposition of cobalt-containing films.